A motion transmission system in a bicycle comprises a chain extending between toothed wheels associated with the axle of the pedal cranks and with the hub of the rear wheel. When there is more than one toothed wheel at at least one of the axle of the pedal cranks and the hub of the rear wheel, and the motion transmission system is therefore provided with a gearshift, a front derailleur and/or a rear derailleur are provided for. In the case of an electronically servo-assisted gearshift, each derailleur comprises a chain guide element, also known as cage, movable to move the chain among the toothed wheels in order to change the gear ratio, and an electromechanical actuator to move the chain guide element. The actuator in turn typically comprises a motor, typically an electric motor, coupled with the chain guide element through a linkage such as an articulated parallelogram, a rack system or a worm screw system, as well as a sensor of the position, speed and/or acceleration of the rotor or of any moving part downstream of the rotor, down to the chain guide element itself. It is worthwhile noting that slightly different terminology from that used in this context is also in use.
Control electronics changes the gear ratio automatically, for example based on one or more detected variables, such as the travel speed, the cadence of rotation of the pedal cranks, the torque applied to the pedal cranks, the slope of the travel terrain, the heart rate of the cyclist and similar, and/or, of particular interest for the present invention, the gear ratio is changed based on commands manually input by the cyclist through suitable control members, for example levers and/or buttons.
A device for controlling the front derailleur and a device for controlling the rear derailleur—or just one of the two in the case of simpler gearshifts—are mounted so as to be easy for the cyclist to manoeuvre, normally on the handlebars, close to the handgrips thereof where the brake lever is also located for controlling the front and rear wheel brake, respectively. Control devices that allow to drive both a derailleur in the two directions and a brake are commonly called integrated controls.
By convention, the device for controlling the front derailleur and the brake lever of the front wheel are located close to the left handgrip, and vice-versa the device for controlling the rear derailleur and the brake lever of the rear wheel are located close to the right handgrip.
The aforementioned components are located on-board the bicycle and must communicate with one another. Moreover, the aforementioned components must be powered.
U.S. Pat. No. 6,741,045 B2 discloses a bicycle control apparatus comprising a bicycle component control unit having one of a control transmitter and a control receiver; a computer control unit having the other one of the control transmitter and the control receiver; a transmission path coupled to the bicycle component control unit and to the computer control unit; wherein the control transmitter communicates power and data to the control receiver on the transmission path.
U.S. Pat. No. 6,757,567 B2 discloses an electronic control system for cycles for association with a set of sensors, a set of actuators and a set of control members associated with the cycle, comprising: a first processor unit able to act as a unit for processing and displaying information; a second processor unit able to act as a unit for controlling the communication and interfacing with said set of control members; and a third processor unit able to act as a unit for interfacing with said set of sensor and said set of actuators; said first, second and third processor unit being connected together via asynchronous bi-directional communication channels.
EP 2 072 091 B1 discloses a bicycle electronic apparatus comprising an electronic control unit, a display unit, a drive unit and a second electronic control unit or sensor unit that communicate via a communication channel through a suitable communication protocol; a line for powering the components of the bicycle electronic apparatus is also provided.
The Applicant has perceived that the architectures of the aforementioned documents generally comprise a main processor, the malfunctioning of which results in the entire system malfunctioning.
The problem at the basis of the invention is therefore that of avoiding the aforementioned drawbacks, in particular providing a bicycle electronic system having a distributed architecture.